Cardiac arrythmias are a major clinical health problem. We have developed a significant and unique solution. We have designed and constructed a novel prototype system which integrates, in real-time, all image and associated physiological variables, device signals and computer generated data derived therefrom required for accurate and precise navigation and targeting in catheter-based ablation of cardiac arrhythmias. The system will render obsolete or unnecessary current approaches to treatment of cardiac arrhythmias, including present ablation methods, open chest surgery and pacemakers and medications in the many cases they don't work. The system design is open and flexible, permitting ready integration of new imaging modalities, interventional devices and physiologic signals as they become available. This system has achieved, for the first time, real-time performance in fusing dynamic cardiac anatomy with physiologic signals. Based on preliminary progress, we now can specify the enhancements required for seamless clinical implementation and application. These improvements include hardware upgrades for performance optimization and interface expansion, new and advanced algorithms for segmentation and registration, precise interactive catheter-to-anatomy navigation using image-guided robotic manipulators, and continuous tracking of respiratory and cardiac cycles for more precise mapping of physiology to anatomy, with more accurate rendering and display of time-patient-specific models of the heart throughout the cardiac cycle. We propose to thoroughly evaluate the enhanced system in both animal experiments and human studies. During this evaluation we will refine and optimize the user interface and procedure flow. We will then specify and assemble a "production" system fully compatible with the clinical procedure room. This production unit will be reproducible and transportable. The multi-disciplinary team of biomedical engineers, cardiologists, radiologists and computer scientists will continue to focus on atrial fibrillation where current treatment strategies are especially ineffective. But the system will be readily adaptable to treatment of any cardiac arrythmias that can be reached by a catheter. This system will herald a new generation of technology for treatment of cardiac arrhythmias resulting in significant clinical benefits, including reduced morbidity, mortality, procedure time, x-ray exposure and cost, with dramatically improved performance and outcomes.